Search

The effect of Sr2+ ions on the microstructure and high frequency properties of 2.5 wt% Bi2O3 added to Co(2)Z hexaferrites (3Ba(1-x)SrxO•2CoO•12Fe2O3, x = 0.0, 0.2, 0.4 and 0.6) synthesised using the solid-state reaction method was investigated. Experimental results indicate that the dielectric properties were markedly enhanced with the increase in the content of Sr2+ ions, thereby increasing the miniaturisation factor, which enables a size reduction in a long frequency range. Slight changes to saturation magnetisation (Ms) and coercivity (Hc) were observed, i.e., the saturation magnetisation (Ms) decreased from 39.99 to 38.11 emu/g, and coercivity (Hc) increased from 59.05 to 65.21 Oe when x increased from 0.0 to 0.6. Meanwhile, ε′ increased from approximately 8 to 12, indicating the invariability in μ′. In addition, the processed materials exhibit relatively low magnetic loss and dielectric loss (magnetic loss tanδμ ≈ 0.08 and dielectric loss (tanδε ≈ 0.007)). These results indicate that the substituted CO(2)Z ferrites have excellent potential in high-frequency antenna applications.

Six new aromatic acids (1–6) and three new leucine derivatives containing an unusual oxime moiety (7–9) were isolated and identified from the deep-sea-derived actinomycetes strain Streptomyces chumphonensis SCSIO15079, together with two known compounds (10–11). The structures of 1–9 including absolute configurations were determined by detailed NMR, MS, and experimental and calculated electronic circular dichroism spectroscopic analyses. Compounds 1–9 were evaluated for their antimicrobial and cytotoxicity activities, as well as their effects on intracellular lipid accumulation in HepG2 cells. Compounds 3 and 4, with the most potent inhibitory activity on intracellular lipid accumulation at 10 μM, were revealed with potential antihyperlipidemic effects, although the mechanism needs to be further studied.

The mangrove-sediment-derived actinomycete strain Streptomyces psammoticus SCSIO NS126 was found to have productive piericidin metabolites featuring anti-renal cell carcinoma activities. In this study, in order to explore more diverse piericidin derivatives, and therefore to discover superior anti-tumor lead compounds, the NS126 strain was further fermented at a 300-L scale under optimized fermentation conditions. As a result, eight new minor piericidin derivatives (piericidins L-R (1–7) and 11-demethyl-glucopiericidin A (8)) were obtained, along with glucopiericidin B (9). The new structures including absolute configurations were determined by spectroscopic methods coupled with experimental and calculated electronic circular dichroism. We also proposed plausible biosynthetic pathways for these unusual post-modified piericidins. Compounds 1 and 6 showed selective cytotoxic activities against OS-RC-2 cells, and 2–5 exhibited potent cytotoxicity against HL-60 cells, with IC50 values lower than 0.1 μM. The new piericidin glycoside 8 was cytotoxic against ACHN, HL-60 and K562, with IC50 values of 2.3, 1.3 and 5.5 μM, respectively. The ability to arrest the cell cycle and cell apoptosis effects induced by 1 and 6 in OS-RC-2 cells, 2 in HL-60 cells, and 8 in ACHN cells were then further investigated. This study enriched the structural diversity of piericidin derivatives and confirmed that piericidins deserve further investigations as promising anti-tumor agents.

A pair of novel lipopeptide epimers, sinulariapeptides A (1) and B (2), and a new phthalide glycerol ether (3) were isolated from the marine algal-associated fungus Cochliobolus lunatus SCSIO41401, together with three known chromanone derivates (4–6). The structures of the new compounds, including the absolute configurations, were determined by comprehensive spectroscopic methods, experimental and calculated electronic circular dichroism (ECD), and Mo2 (OAc)4-induced ECD methods. The new compounds 1–3 showed moderate inhibitory activity against acetylcholinesterase (AChE), with IC50 values of 1.3–2.5 μM, and an in silico molecular docking study was also performed.

The annual cumulative quantity of high and medium alloy steel scrap has exceeded 10 million tons. Using the traditional smelting process involving electric arc refining in a smelting furnace for these scraps causes high percentages of alloy losses, which decreases the value of the alloy steel scrap and poses environmental threats. Existing studies have rarely focused on separate smelting of the scrap and oxidation behaviors of the alloying elements. Therefore, this study proposes an induction melting and electroslag remelting scheme to process the scrap. Based on this scheme, the effects of the temperature, oxygen content, and element contents on the recovery percentages of the alloying elements were investigated using pilot experiment and thermodynamic analysis. The experimental results showed that the alloying elements (tungsten, chromium, nickel, molybdenum, and vanadium) exhibited recovery percentages of 97.36%, 94.62%, 97.63%, 95.09%, and 89.49%, respectively; furthermore, the impurity content did not increase during smelting. The thermodynamic analysis indicated that an increase in carbon content improved the oxidation resistance of the alloying elements except for nickel, whereas the increases in the contents of oxygen and alloying elements increase their oxidation. Steam partial pressure and air suction dramatically increase the concentrations of nitrogen, hydrogen and oxygen. This scheme is an alternative for smelting medium and high alloy steel scrap, and the thermodynamic analysis provides a theoretical understanding of the oxidation behaviors of the alloying elements in the steel scrap and the control of impurity.

To reduce energy and resource consumption, high-strength hot-rolled rebars with yield strengths of ≥400 MPa (HRB500) and ≥500 MPa (HRB600) have been designed and produced in recent years. Optimizing the microstructure in the steel to improve strength necessitates determining the kinetics of the phase transition of austenite to polygonal ferrite. Therefore, in the study, the effect of temperature and holding time on the volume fraction of ferrite is investigated in HRB500 and HRB600 steels. Experimental results show that the ferrite percentage initially increases with an increase in temperature and then decreases as the temperature increases from 600 to 730 °C. The optimum temperature range is 680–700 °C for HRB500 steel and 650–680 °C for HRB600 steel. Based on the Johnson–Mehl–Avrami equation, phase transition kinetic models are established. Model predictions are consistent with the validation data. Thus, this study establishes a reference for studying ferrite formation during cooling.